focalboard/website/site/static/css/markdown.css

table {
    padding: 0;
}

table tr {
    border-top: 1px solid #cccccc;
    background-color: white;
    margin: 0;
    padding: 0;
}

table tr:nth-child(2n) {
    background-color: #f8f8f8;
}

table tr th {
    font-weight: bold;
    border: 1px solid #cccccc;
    text-align: left;
    margin: 0;
    padding: 6px 13px;
}

table tr td {
    border: 1px solid #cccccc;
    text-align: left;
    margin: 0;
    padding: 6px 13px;
}

table tr th :first-child, table tr td :first-child {
    margin-top: 0;
}

table tr th :last-child, table tr td :last-child {
    margin-bottom: 0;
}